The present invention relates to aircraft airflow control devices, for example, devices for retarding airspeed and/or bringing aboard external airflow.
FIG. 1A is a partially schematic plan view of a typical commercial transport aircraft 10 in accordance with the prior art. The aircraft 10 includes a fuselage 20 and swept wings 11 carrying primary engines 12. Each wing 11 can include at least one wing speed brake 50 to reduce aircraft airspeed, for example, during normal descent and landing approach, or during an emergency descent. Alternatively, the aircraft 10 can include a fuselage-mounted speed brake 50a to perform the same functions.
The aircraft 10 can also include an environmental control system (ECS) pack 30 that supplies conditioned, pressurized air to the aircraft cabin. In a typical installation, the ECS pack 30 can receive pressurized air bled from the compressors of the primary engines 12 and delivered to the ECS pack 30 via compressor bleed air ducts 31. The ECS pack 30 can condition the air (for example by filtering and/or cooling the air) before delivering the air to the cabin via an ECS supply duct 32. The ECS pack 30 can be cooled with external cooling air supplied by a cooling air inlet duct 33. The cooling air can exit the aircraft 10 via a cooling air exhaust duct 34.
The aircraft 10 can further include an auxiliary power unit (APU) 40. One function performed by the APU 40 is to supply pressurized air to the ECS pack 30 when the primary engines 12 are not doing so. Accordingly, the APU 40 can include a gas turbine that receives air through an APU inlet duct 41. The APU inlet duct 41 receives air from a deployable APU inlet scoop 42, which is normally flush with the aircraft fuselage 20 when the APU 40 is not running, and is deployed outwardly to capture air for the APU inlet duct 41 when the APU 40 is operating. The APU combustion products exit the aircraft 10 via an APU exhaust duct 43, and pressurized air is bled from the APU 40 and supplied to the ECS pack 30 via an APU bleed duct 44. Accordingly, the APU 40 can supply pressurized air for distribution to the cabin in lieu of or in addition to pressurized air supplied by the primary engines 12.
FIG. 1B is a partially schematic, cross-sectional view of the fuselage 20 of the aircraft 10 taken substantially along line 1Bxe2x80x941B of FIG. 1A. As shown in FIG. 1B, the fuselage 20 houses a cabin area 21 positioned above a cargo area 22. The ECS supply duct 32 supplies pressurized air to the cabin area 21 to maintain a pressurized environment within the cabin area 21. Typically, the cabin area 21 is kept at a pressure-altitude of about 8,000 feet (i.e., a pressure corresponding to the standard pressure at an altitude of 8,000 feet). The air supplied to the cabin area 21 also passes downwardly to the cargo area 22. A portion of the pressurized air is then dumped overboard via an exhaust valve 25. Air remaining in the cargo area 21 can then be returned to the ECS pack 30 via a pump 24 and an ECS return duct 35. The ECS pack 30 can supplement the recycled air with make-up air from the compressor bleed ducts 31 (FIG. 1A) and return the pressurized air to the cabin area 21. The cargo area 22 can further include floor release valves 26 (such as upwardly opening floor panels) that can relieve pressure in the cargo area 22 in the event that the cargo area 22 becomes overpressurized.
One goal of the commercial aircraft transport industry is to convey passengers and cargo as quickly as possible from one point to another. As the speeds of commercial aircraft have increased, the cruising altitudes of these aircraft have also increased to maintain overall flight efficiency. One drawback with increasing aircraft altitude is that it can increase the likelihood of exposing passengers to very low air pressures in the event the cabin area 21 becomes depressurized. For example, if a window 23 of the fuselage 20 fails, the pressure within the fuselage 20 can rapidly decrease. Accordingly, Federal Aviation Regulations (FARs) require that for selected depressurization events, the aircraft passengers and crew be exposed to pressure-altitudes of greater than 25,000 feet for a period not to exceed two minutes.
As the cruising altitude for aircraft increases, meeting the foregoing requirement presents at least two difficulties. For example, as the aircraft operate in increasingly thinner atmospheric conditions, the aircraft systems must become larger and/or significantly more efficient to maintain cabin pressure during a depressurization event. Furthermore, the time required to descend from a high cruise altitude to an altitude below 25,000 feet increases significantly. Existing speed brake systems are typically inadequate to allow an aircraft to rapidly descend from an altitude of 40,000 feet or higher, and ECS packs must be substantially increased in size and weight to adequately pressurize the cabin area during a descent following a depressurization event.
The present invention is directed toward methods and apparatuses for controlling aircraft airflow. An apparatus in accordance with one aspect of the invention includes an air scoop having an inlet and an outlet and being configured to mount to the aircraft to be movable relative to at least a portion of the aircraft between a first position and a second position. The air scoop can be oriented to capture air when in the second position, and the outlet can be configured to be coupled in fluid communication with a pressurized portion of the aircraft when the air scoop is in the second position to convey air from the inlet to the pressurized portion. The air scoop can be configured to significantly increase the drag of the aircraft from a first value when the air scoop is in the first position to a second value when the air scoop is in the second position. Accordingly, in one aspect of the invention, the air scoop can increase the descent rate of the aircraft and provide pressurization for the interior of the aircraft.
In a further aspect of the invention, the apparatus can include a valve in fluid communication with the air scoop. The valve can be changeable from a first configuration to a second configuration with the valve being positioned to pass none of the captured air or a first quantity of the captured air toward the pressurized portion of the aircraft when in the first configuration, and with the valve positioned to pass a second quantity of the captured air toward the pressurized portion when in the second configuration, with the second quantity being greater than the first quantity. The apparatus can further include a latch member operatively coupled to the valve and movable between a first latch position and a second latch position, with the latch member at least restricting a change in configuration of the valve when the latch member is in the first latch position, and allowing a change in the configuration of the valve when the latch member is in the second latch position. A pressure sensor can be operatively coupled to the latch member to move the latch member from the first position to the second position when a pressure within the pressurized portion falls below a selected value. Accordingly, the latch can allow pressurization of the aircraft following a depressurization event, and can lock out operation of the valve, for example, during a normal descent.
The invention is also directed toward a method for controlling aircraft airflow. In one aspect of the invention, the method can include significantly increasing a drag of the aircraft by moving an air scoop from a first position to a second position. The method can further include conveying at least a portion of the air intercepted by the air scoop to a pressurized portion of the aircraft. In a further aspect of the invention, air captured by the air scoop can be directed into a cargo portion of the fuselage and then from the cargo portion to a cabin portion of the fuselage. In still another aspect of the invention, the air captured by the air scoop can be directed into the pressurized portion of the aircraft, bypassing the primary engines, auxiliary power units, and/or environmental control systems before entering the pressurized portion. Accordingly, the air scoop can operate to pressurize the aircraft independently of the bypassed systems.